1. Field of the Invention
The invention relates to panel insulation systems. More particularly, it relates to relieving the thermal strain in vacuum panel insulation systems exposed to large temperature differences.
2. Description of the Prior Art
Vacuum panel insulation systems have been practiced in many forms in the art. Such systems are desirable since they can be easily fitted to odd shapes, can be made lightweight, provide easy maintenance, and can be mass produced at low cost. When subjected to large temperature differences, however, thermal strains are developed in the vacuum envelope and in the internal insulation. These result in undesired warpage and/or breakage of the panel due to the temperature difference between the top and bottom surfaces thereof, and to the joining together of the top and bottom edges of the panel in a rigid manner.
In light of such warpage problems, panels have been designed with a variety of edge sections in an attempt to decouple the hot and cold sections thereof. Edge sections have been proposed in the form of corrugated bellows, and shallow edge angles have been proposed, but have not been found to be workable for large thin panels subjected to large temperature differences. In this regard, it should be understood that the thickness of typical vacuum insulation panels ranges from 1/4" to 1". Fabricating an expansion joint in this small distance to accommodate movements of 1/8" to 1/2" is extremely difficult. As a result, the size of vacuum panels has been limited by such problems associated with the design of the edge expansion joints thereof.
It is an object of the invention therefore, to provide an improved panel insulation system.
It is another object of the invention to provide vacuum panels overcoming the warpage caused by thermal strains when subjected to large temperature differences.
With these and other objects in mind, the invention is hereinafter described in detail, the novel features thereof being particularly pointed out in the appended claims.